Web/API/ResizeObserverEntry/contentRect

The contentRect read-only property of the ResizeObserverEntry interface returns a DOMRectReadOnly object containing the new size of the observed element when the callback is run. Note that this is better supported than ResizeObserverEntry.borderBoxSize or ResizeObserverEntry.contentBoxSize, but it is left over from an earlier implementation of the Resize Observer API, is still included in the spec for web compat reasons, and may be deprecated in future versions.

Syntax

var contentRect = resizeObserverEntry.contentRect;

Value

A DOMRectReadOnly object containing the new size of the element indicated by the target property.

If the target is an HTML Element, the returned contentRect is the element's content box. If the target is an SVGElement, the returned contentRect is the SVG's bounding box.

Examples

The following snippet is taken from the [[../../../../../../../mdn.github.io/dom-examples/resize-observer/resize-observer-text|resize-observer-text.html]] (see source) example. This uses a simple feature detection test to see if the browser supports the newer ResizeObserverEntry.contentBoxSize property — if so, it uses that to get the sizing data it needs. If not, it uses contentRect.

const resizeObserver = new ResizeObserver(entries => {
  for (let entry of entries) {
    if(entry.contentBoxSize) {
      h1Elem.style.fontSize = Math.max(1.5, entry.contentBoxSize.inlineSize/200) + 'rem';
      pElem.style.fontSize = Math.max(1, entry.contentBoxSize.inlineSize/600) + 'rem';
    } else {
      h1Elem.style.fontSize = Math.max(1.5, entry.contentRect.width/200) + 'rem';
      pElem.style.fontSize = Math.max(1, entry.contentRect.width/600) + 'rem';
    }
  }
});

resizeObserver.observe(divElem);

Specifications

Specification	Status	Comment
Resize ObserverThe definition of 'contentRect' in that specification.	Editor's Draft	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`contentRect`	Chrome Full support 64	Edge Full support 79	Firefox Full support 69	IE No support No	Opera Full support Yes	Safari No support No	WebView Android Full support 64	Chrome Android Full support 64	Firefox Android No support No	Opera Android Full support Yes	Safari iOS No support No	Samsung Internet Android Full support 9.0

Legend

Full support: Full support
No support: No support

ResizeObserverEntry.contentRect by Mozilla Contributors is licensed under CC-BY-SA 2.5.